1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a so-called in-plane electric field type of liquid crystal display (LCD) device or a so-called in plane switching (IPS) type of liquid crystal display device.
2. Description of the Related Art
A so-called in-plane electric field type of liquid crystal display device is constituted such that pixel electrodes and counter electrodes which generate an electric field therebetween are formed on pixel regions at a liquid-crystal-side surface of one of the respective substrates which are arranged to face each other by way of a liquid crystal and the liquid crystal is responsive to components of the electric field substantially parallel to the substrates.
In an active matrix type of liquid crystal display device adopting such a constitution, first of all, on the liquid-crystal-side surface of the above-mentioned one substrate, respective regions which are surrounded by a plurality of gate signal lines which are arranged in parallel and a plurality of drain signal lines which cross these respective gate signal lines and are arranged in parallel are formed as pixel regions.
Here, each pixel region is provided with a thin film transistor which is operated in response to a scanning signal from the gate signal line, the pixel electrode to which a video signal is supplied from the drain signal line through the thin film transistor, and the counter electrode to which a signal which becomes the reference with respect to the video signal is supplied.
Here, the pixel electrodes and the counter electrodes are respectively formed in a strip-shaped pattern which extend in one direction and these respective electrodes are formed of two pieces or more in number and are usually arranged alternately.
Further, with respect to such a constitution, there has been also known a constitution in which the counter electrodes are formed on upper surfaces of insulation films which are formed so as to cover the drain signal lines, and the drain signal lines and the center axes of the insulation films are substantially aligned, and the insulation films have a width larger than a width of the drain signal lines, and the insulation films are formed along the drain signal lines.
Such a constitution is provided for facilitating an electric line of force from the drain signal lines to terminate at the counter electrodes arranged above the drain signal lines and for preventing the electric line of force from terminating at the pixel electrodes. When the electric line of force terminates at the pixel electrodes, this gives rise to noises.
On the other hand, the liquid crystal display device having such a constitution requires counter voltage signal lines for supplying a signal to the counter electrodes and the counter voltage signal lines are arranged to run within the pixel regions so that there has been a drawback that the counter voltage signal lines impede the enhancement of a so-called numerical aperture of the pixel region.
Further, the counter electrodes and the counter voltage signal lines are arranged by way of an insulation layer in many cases and the electrical connection between the counter electrodes and the counter voltage signal lines is established via small through holes formed in the insulation layer and hence, the further enhancement of the reliability of connection has been requested. This coincides with the demand for high definition in recent years.